A better understanding of pregnancy desires is critical for reducing unintended pregnancy. Current state-of- the-art conceptualization and measurement of pregnancy desires suffer from serious limitations that dramatically undermine our ability to understand the processes that link pregnancy desires and subsequent pregnancy. The proposed project includes at least three major innovations: (1) thirteen detailed and nuanced measures of pregnancy desire; (2) measures of perceptions of partners' pregnancy desires across all relationships in the period of observation (including short-lived and/or unstable relationships); (3) weekly measures of all aspects of pregnancy desire, representing the dynamics in these desires. We propose to improve conceptualization, measurement, and understanding of pregnancy desires via four specific aims: 1. Investigate the Measurement Properties of Pregnancy Desires 2. Analyze the Role of Perceptions of Partners' Pregnancy Desires 3. Describe and Predict the Dynamics of Pregnancy Desires 4. Estimate the Influence of Dynamic Pregnancy Desires on Subsequent Pregnancy We propose to use a unique dataset from the Relationship Dynamics and Social Life (RDSL) study. RDSL began with a face-to-face baseline survey of 1,003 18- and 19-year-old women. Over the next 2.5 years, these women provided weekly updates about their desires for pregnancy and about experiences with pregnancy, relationships, contraceptive use, and related attitudes. Over the 2.5-year study period, which ended in February, 2012, the young women reported 233 pregnancies. The analyses proposed here were not part of the original RDSL proposal.